THURSDAY, May 16 (HealthDay News) -- There are few things more inviting than a cool, clear pool on a hot summer day. But a new federal report will have you thinking twice before dipping a toe in the water.

Fifty-eight percent of pool filter samples taken from Atlanta area pools last summer contained E. coli, a bacteria found in human feces.

The report is a sign that swimmers often contaminate pool water when they have a "fecal incident" in the water, or when human waste washes off their bodies because they don't shower thoroughly before hitting the water, according to the report from the U.S. Centers for Disease Control and Prevention.

And while the study only focused on pools in the Atlanta region, the researchers said it's likely that fecal contamination from swimmers is a problem in public pools throughout the country. The study did not look at water parks, residential pools or other types of recreational water.

"Swimming is an excellent way to get the physical activity needed to stay healthy," Michele Hlavsa, chief of the CDC's Healthy Swimming Program, said in an agency news release. "However, pool users should be aware of how to prevent infections while swimming.

"Remember," she added, "chlorine and other disinfectants don't kill germs instantly. That's why it's important for swimmers to protect themselves by not swallowing the water they swim in and to protect others by keeping feces and germs out of the pool by taking a pre-swim shower and not swimming when ill with diarrhea.

The CDC says all swimmers should take the following steps to keep feces out of pools and to prevent infections:

Don't swim if you have diarrhea.

Shower with soap before swimming.

Take a rinse shower before getting back in the water.

Go to the bathroom every 60 minutes.

Wash your hands with soap after using the toilet or changing diapers.

Don't swallow the water you swim in.

Parents of young children should take the following steps:

Take children on bathroom breaks every 60 minutes or check diapers every 30 to 60 minutes.

Change diapers in the bathroom or diaper-changing area and not at poolside where germs can rinse into the water.

Dr. Robert Glatter, an emergency medicine physician at Lenox Hill Hospital in New York City, said the new study "highlights the importance of practicing good hygiene anytime we swim in a pool, since the potential for contamination with fecal organisms, which could lead to severe diarrheal illnesses, remains an ever present concern.

"From a public health standpoint," he added, "it is especially important for people to avoid swimming when they have diarrhea, as other swimmers could swallow germ-laden water and potentially become ill.

The study reveals a "true public health concern, and reinforces the need to practice safe and effective swim hygiene as the summer approaches," Glattner said.

The study appears in the May 17 issue of the CDC's Morbidity and Mortality Weekly Report. Its release is timed in advance of Recreational Water Illness and Injury Prevention Week, May 20-26. The goal of the prevention week is to "raise awareness about healthy swimming, including ways to prevent recreational water illnesses (RWIs). Germs that cause RWIs are spread by swallowing, breathing in the mists or aerosols from, or having contact with contaminated water in swimming pools, water parks, hot tubs, interactive fountains, water play areas, lakes, rivers, or oceans," according to the CDC.